The present invention relates to communication devices, communication systems and methods of communicating, and more particularly to radio frequency communication devices.
Electronic identification systems typically comprise two devices which are configured to communicate with one another. Preferred configurations of the electronic identification systems are operable to provide such communications via a wireless medium.
One such configuration is described in U.S. patent application Ser. No. 08/705,043, filed Aug. 29, 1996 now U.S. Pat. No. 6,130,602, assigned to the assignee of the present application and incorporated herein by reference. This application discloses the use of a radio frequency (RF) communication system including communication devices. The disclosed communication devices include an interrogator and a transponder, such as a tag or card.
Such communication systems can be used in various identification functions and other applications. The interrogator is configured to output a polling signal which may comprise a radio frequency signal including a predefined code. The transponders of such a communication system are operable to transmit an identification signal responsive to receiving an appropriate command or polling signal. More specifically, the appropriate transponders are configured to recognize the predefined code. The transponders receiving the code subsequently output a particular identification signal which is associated with the transmitting transponder. Following transmission of the polling signal, the interrogator is configured to receive the identification signals enabling detection of the presence of corresponding transponders.
Such communication systems are useable in identification applications such as inventory or other object monitoring. For example, a remote identification device is attached to an object of interest. Responsive to receiving the appropriate polling signal, the identification device is equipped to output an identification signal. Generating the identification signal identifies the presence or location of the identification device and the article or object attached thereto.
It is preferred to maximize communication range between communication devices of the identification system while providing robust communications. Increasing the range also increases the applications of the identification system. Providing robust communications ensures reliability and integrity of the system.
However, limitations exist upon the wireless communication components utilized within the communication devices. For example, given the nature of use of such electronic devices (i.e., attachment of the transponder to other devices or objects), it is preferred to minimize the size of the electronic device. Compact electronic devices also have cosmetic and utilitarian advantages over larger conventional communication devices. Size limitations impose limitations upon the wireless communication components themselves. In addition, the Federal Communication Commission also imposes power limits upon the wireless communication components.
Therefore, it is desirable to provide an identification device which achieves the benefits of increased range and robust wireless communications in consideration of size and power limitations.
According to one aspect, the present invention provides a communication device including a first antenna operable to receive wireless communication signals and a second antenna having plural leads and operable to output wireless communication signals. The communication device further comprises a connection coupled with the second antenna and a switch. The switch is operable to provide selective shorting, and insulation or electrical isolation of leads of the second antenna. The connection provides low load impedance of the second antenna during receiving of wireless communication signals in a preferred embodiment of the invention.
According to some embodiments of the invention, the communication devices comprise one of a radio frequency identification device and a remote intelligent communication device.
Another communication device of the present invention includes a first antenna operable to receive wireless communication signals and a second antenna operable to output wireless communication signals. The second antenna is selectively configured between high load impedance and low load impedance. The communication device includes a switch selectively operable to electrically short and insulate the leads. Further, a transformer is provided intermediate the switch and the second antenna and the transformer is configured to provide low load impedance of the second antenna responsive to the switch being open.
The present invention also provides a communication system including an interrogator and a communication device configured to communicate with the interrogator. The communication device includes a first antenna operable to receive wireless signals from the interrogator and a second antenna operable to output wireless signals to the interrogator. The communication device also includes a connection configured to provide a low load impedance of the second antenna during receiving of wireless signals using the first antenna.
One method of communicating according to the present invention includes forming a first antenna, forming a second antenna, receiving wireless interrogation signals using the first antenna and outputting wireless identification signals using the second antenna. The method also provides opening a coupling intermediate plural leads of the second antenna during the receiving, selectively shorting the leads of the second antenna during the outputting, and providing a low load impedance of the second antenna during the receiving. Methods according to additional aspects of the invention also provide beam forming using the first and second antennas.